The impact of temperature on the production and fitness of microsclerotia of the fungal bioherbicide Mycoleptodiscus terrestris

The impact of growth temperature was evaluated for the fungal plant pathogen Mycoleptodiscus terrestris over a range of temperatures (20 368C). The effect of temperature on biomass accumulation, colony forming units (cfu), and microsclerotia production was determined. Culture temperatures of 24 308C produced significantly higher biomass accumulations and 20 248C resulted in a significantly higher cfu. The growth of M. terrestris was greatly reduced at temperatures above 308C and was absent at 368C. The highest microsclerotia concentrations were produced over a wide range of temperatures (20 308C). These data suggest that a growth temperature of 248C would optimize the parameters evaluated in this study. In addition to growth parameters, we also evaluated the desiccation tolerance and storage stability of air-dried microsclerotial preparations from these cultures during storage at 48C. During 5 months storage, there was no significant difference in viability for air-dried microsclerotial preparations from cultures grown at 20 308C ( 72% hyphal germination) or in conidia production (sporogenic germination) for air-dried preparations from cultures grown at 20 328C. When the effect of temperature on germination by air-dried microsclerotial preparations was evaluated, data showed that temperatures of 22 308C were optimal for hyphal and sporogenic germination. Air-dried microsclerotial preparations did not germinate hyphally at 368C or sporogenically at 20, 32, 34, or 368C. These data show that temperature does impact the growth and germination of M. terrestris and suggest that water temperature may be a critical environmental consideration for the application of air-dried M. terrestris preparations for use in controlling hydrilla.